ZF-8898: Handling xmlrpc i8 Tags

Description

When i receive a xmlrpc respose with a i8 tag inside, Zend can't print this value !!! I have attached a patch File that fixed this problem

Comments

Patch File to Fix I8 Tag handling

As discussed in #zftalk.dev i refactored Zend_XmlRpc_Value_BigInteger because some major bugs made this class unusable.

Because of some big mistakes in Zend_XmlRpc_Value_BigInteger and it's tests it was not possible to not break backward compatibility.

Fixed in r23363.

Only tests are merged to branch, Should be done the merged of the correction also or revert tests flawed of the branch already that this issue break BC.